Status of the fuel stress and failure rate calculations at KFA

Bongartz, K.

Book/Report

FZJ-2016-04506

Status of the fuel stress and failure rate calculations at KFA

Bongartz, K. (Corresponding author)FZJ*

1980
Kernforschungsanlage Jülich, Zentralbiliothek, Verlag Jülich

Jülich : Kernforschungsanlage Jülich, Zentralbiliothek, Verlag, Berichte der Kernforschungsanlage Jülich 1686, 15 p. 5 Fig. (1980)

Please use a persistent id in citations: http://hdl.handle.net/2128/12246

Report No.: Juel-1686

Abstract: The basic unit of the fuel in the core of a High Temperature Reactor (HTR) with block or spherical fuel, elements is the coated particle. These coated particles consist of small spherical pyrocarbon (PyO) and siliconcarbide (SiC) coated fuel kernels. High stresses may be induced into the coatings during irradiation due to the fission gas pressure, the irradiation induced dimensional changes of the PyC layers and the kernel swelling. A schematic description of the coated particle is given in figure 1. It has the fuel kernel 200 - 800 $\mu$m in diameter. This is surrounded by a porous PyC layer 30 -100 $\mu$m thick, the so-called buffer layer which has to accommodate the fission gases and recoils. Then follows another coating shell. It may either consist of one dense PyC layer with a thickness of ~ 100 $\mu$m (BISO particle) or a combination of two dense PyC layers, with a thickness of ~ 35 $\mu$m each and a SiC interlayer with a thickness of ~ 35 $\mu$m (TRISO particle). The outer coating shell combination PyC-SiC-PyC acts as a pressurevessel for the fission gases, and a diffusion barrier for the solid fission products. The SiC interlayer improves the retention of the solid fission products as well as the mechanical stability of the shell (1) (2). In order to optimize the coated particle with respect to its mechanical performance it is desirable to have a model to predict the stresses in the coating during irradiation. Several models (3) (4) have been established for this purpose. The model used at KFA up to now was established by H. Walther (5) (6). A computer programme based on this model calculates coating stresses in BISO and TRISO particles. [...]

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